Inner Housing for a Turbomachine

ABSTRACT

A three-shell steam turbine is provided. The three-shell steam turbine includes an outer housing, an outer inner housing and an inner inner housing, wherein the outer inner housing is arranged around the inner inner housing, in such a way that a cooling steam chamber is formed in between and a flow duct is formed between the outer inner housing and the rotor.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US National Stage of International ApplicationNo. PCT/EP2009/064492, filed Nov. 3, 2009 and claims the benefitthereof. The International Application claims the benefits of EuropeanPatent Office application No. 08019820.3 EP filed Nov. 13, 2008. All ofthe applications are incorporated by reference herein in their entirety.

FIELD OF INVENTION

The invention relates to a turbomachine, comprising a rotor which ismounted such that it can rotate about a rotation axis, an inner innerhousing and an outer inner housing which are arranged around the rotor,and an outer housing which is arranged around the inner and the outerinner housings, wherein the outer inner housing is arranged around theinner inner housing along the rotation axis, wherein the outer innerhousing is arranged around the inner inner housing along the rotationaxis, wherein a first flow area for a flow medium to flow in a flowdirection is formed between the inner inner housing and the rotor, andwherein a second flow area is formed between the outer inner housing andthe rotor downstream from the first flow area, seen in the flowdirection.

BACKGROUND OF INVENTION

By way of example, a turbomachine means a steam turbine. A steam turbinenormally has a rotor, which is mounted such that it can rotate, and ahousing which is arranged around the rotor. A flow channel is formedbetween the rotor and the inner housing. The housing in a steam turbinehas to be able to carry out a number of functions. On the one hand, thestator blades in the flow channel are arranged on the housing and, onthe other hand, the inner housing must withstand the pressures and thetemperatures of the flow medium for all load and special operatingsituations. In the case of a steam turbine, the flow medium is steam.Furthellnore, the housing must be designed such that inputs and outputs,which are also referred to as bleeds, are possible. A further functionwhich a housing must carry out is the capability to allow a shaft end topass through the housing.

With the high stresses, pressures and temperatures which occur duringoperation, it is necessary for the materials to be suitably chosen andfor the design to be chosen such that the mechanical integrity andfunctionality are made possible. For this purpose, it is necessary touse high-quality materials, in particular in the area of the inlet flowand the first stator blade grooves.

Nickel-based alloys are suitable for applications with fresh steamtemperatures of more than 650° C., for example 700° C., since theywithstand the loads which occur at high temperatures. However, the useof a nickel-based alloy such as this is associated with newrequirements. For example, the costs of nickel-based alloys arecomparatively high and, furthermore, the capability to manufacturenickel-based alloys is restricted, for example because the castingcapability is restricted. This means that the use of nickel-basedmaterials must be minimized. Furthermore, nickel-based materials arepoor heat conductors. The temperature gradients across the wallthickness are therefore so great that thermal stresses are comparativelyhigh. Furthermore, it should be noted that the temperature differencebetween the inlet and outlet of the steam turbine rises when usingnickel-based materials.

Various concepts are currently being pursued in order to produce a steamturbine which is suitable for high temperatures and for high pressures.For example, it is known for an inner housing structure, which comprisesa plurality of parts, to be incorporated into an outer housing structureaccording to the article by Y. Tanaka et al.

“Advanced Design of Mitsubishi Large Steam Turbines”, Mitsubishi HeavyIndustries, Power Gen Europe, 2003, Dusseldorf, May 6-8, 2003.

It is likewise known for an inner housing to be formed from two parts,according to DE 10 2006 027 237 A1.

DE 342 1067 likewise discloses a multi-component inner housingstructure, as does DE 103 53 451 A1.

The object of the invention is to offer a further possible way to designan inner housing such that it is suitable for high temperatures andpressures.

SUMMARY OF INVENTION

This object is achieved by the features of the claims. Advantageousdevelopments are specified in the dependent claims.

A major idea of the invention is to design a triple-casing steamturbine. The inner housing is in this case fondled into an inner innerhousing and an outer inner housing. The inner inner housing is arrangedin the area of the inlet-flow area, and must therefore withstand thehigh temperatures and the high pressures. The inner inner housing istherefore formed from a suitable material, for example from anickel-based alloy. The flow channel is formed between the inner innerhousing and the rotor. The inner inner housing therefore has apparatusessuch as grooves, in order to allow stator blades to be fitted therein.An outer inner housing is arranged around the inner inner housing. Theessential feature in this case is that a cooling steam area is createdbetween the inner inner housing and the outer inner housing, and coolingmedium is applied to this area. The outer inner housing is in this casedesigned such that it is adjacent to the inner inner housing, seen inthe flow direction, and represents a boundary of the flow channel, inwhich case apparatuses such as grooves are also provided in the outerinner housing, in order to allow stator blades to be fitted.

A steam which is at a lower temperature and a lower pressure is appliedto the outer inner housing, as a result of which the material of theouter inner housing may be less resistant to heat than the material ofthe inner inner housing. In particular, it is sufficient for the outerinner housing to be formed from a less high-quality material. An outerhousing is arranged around the inner inner housing and the outer innerhousing.

In one advantageous development, a flow connection is provided betweenthe inner inner housing and the outer inner housing, and makes itpossible to feed a cooling medium from the flow channel into the coolingsteam area. This cooling steam is therefore taken from the flow channel,thus allowing the primary stresses and the secondary stresses in theinner inner housing to be kept low. Primary stresses are mechanicalstresses which occur as a result of external loads, for example steampressures, weight forces etc. In contrast, secondary stresses, which arealso referred to as theimal stresses, are mechanical stresses whichoccur as a result of temperature fields which cannot be equalized, orchanges in thermal expansions.

The cooling steam which is located in the cooling steam area can at thesame time be used as insulation from the outer inner housing.Furthermore, a water extraction line is provided, which dissipatescondensed water which occurs when stationary. In a further advantageousdevelopment, the steam turbine is in the form of a twin-flow steamturbine, thus allowing stresses and forces to be optimally matched toone another, for symmetry reasons.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention will be described in thefollowing text with reference to the drawings. These drawings areintended to illustrate the exemplary embodiments, but not to scale, andin fact the drawing, where used for explanatory purposes, is in aschematic and/or slightly distorted form. With respect to additions tothe teachings which can be identified directly from the drawing,reference is made here to the relevant prior art.

In detail, in the drawing:

FIG. 1 shows a section illustration through a twin-flow steam turbine;

FIG. 2 shows a partial section illustration through a steam turbine,seen in the flow direction.

DETAILED DESCRIPTION OF INVENTION

The section illustration shown in FIG. 1 through the turbomachine 1essentially comprises an outer housing 2, an outer inner housing 3,which is arranged within the outer housing 2, and an inner inner housing4, which is arranged within the outer inner housing 3.

A rotor 5 is mounted between the outer inner housing 3 and the innerinner housing 4 such that it can rotate about a rotation axis 6. A flowchannel 7 is formed between the outer inner housing 3 and the rotor 5,as well as between the inner inner housing 4 and the rotor 5. For thesake of clarity, individual rotor blades and stator blades are notillustrated in any more detail. The stator blades are arranged on theinner inner housing 4 and on the outer inner housing 3. The rotor bladesare arranged on the rotor 5 such that the thermal energy of fresh steamcan be converted to rotation energy in the flow channel 7. Fresh steamflows via a fresh-steam inlet area, which is not illustrated in any moredetail, first of all into a first flow area 8, which is arranged betweenthe inner inner housing 4 and the rotor 5.

The inner inner housing 4 is formed from a nickel-based material. Theouter inner housing 3 can be formed from a material which is lessresistant to high temperatures. In one alternative embodiment, the innerinner housing 4 is faulted from a steel with a high chromium content,which comprises 9-10% by weight of chromium, wherein the outer innerhousing 3 is formed from a material of less high quality than the innerinner housing 4.

The steam flowing in the first flow area 8 flows along the flow channel7 in a flow direction 9. The steam turbine 1 illustrated in FIG. 1 is atwin-flow machine, that is to say the steam flows both along a firstpath and along a second path in the first inlet-flow area 8. The outerinner housing 3 is adjacent to the inner inner housing 4. A second flowarea 10 is formed between the outer inner housing 3 and the flow channel7. The outer inner housing 3 comprises apparatuses, for example grooves,for holding the stator blades. The inner inner housing 4 is suspended inthe outer inner housing 3 in a manner which is not illustrated in anymore detail. The outer inner housing is formed around the inner innerhousing 4 in the area of the first flow area 8. The outer inner housing3 is in this case formed around the inner inner housing 4, with respectto the rotation axis 6. Outside the first flow area 8, the outer innerhousing 3 is not arranged around the inner inner housing 4 with respectto the rotation axis 6. The first flow area 8 comprises the flow channelas far as the point at which the inner inner housing 4 ends. A flowconnection 11 is arranged between the inner inner housing 4 and theouter inner housing 3 at the junction area between the first flow area 8and the second flow area 10. Steam which has been expanded from the flowchannel 7 can thus flow via the flow connection 11 into a cooling steamarea 12, which is located between the inner inner housing 4 and theouter inner housing 3. The location of the flow connection 11 musttherefore be appropriately chosen to ensure that a cooling medium at anappropriate temperature and an appropriate pressure flows into thecooling steam area 12 via the flow connection 11. This cooling mediumwhich flows in the cooling steam area 12 insulates the inner innerhousing 4 from the outer inner housing 3. The outer inner housing 3essentially comprises a first outer inner housing upper part and asecond lower outer inner housing part. The outer inner housing 3essentially comprises three sections, which are shaped differently. In afirst section, the inner housing is therefore designed to be essentiallyparallel to the flow channel 9. This first area is designed to be moreor less symmetrical, both in the one path and in the other path. In ajunction area, which is arranged in the vicinity of the flow connection11, the second central area of the outer inner housing 3 is adjacent.This central area is characterized by an alignment which is first of allradial, in order to allow a cooling steam area 12 to be formed betweenthe inner inner housing 4 and the outer inner housing 3.

A water extraction line, which is not illustrated in any detail butdissipates condensed water which occurs when the steam turbine isstationary, is provided, inter alia, in the cooling steam area 12, inorder to protect the steam turbine. FIG. 2 shows an illustration of thesteam turbine 1 in the flow direction. The section illustrated in FIG. 2is approximately in the center 13 of the steam turbine 1. The coolingsteam which is located in the cooling steam area 12 is passed out of thecooling steam area via a cooling steam outlet line. In this case, thecooling steam outlet line is formed by means of a hole in the outerinner housing 3. The cooling steam outlet line 14 is, in particular,arranged in the upper part of the outer inner housing 3.

In an alternative embodiment, the cooling steam outlet line 14 canlikewise be arranged in the lower part of the outer inner housing 3.This alternative cooling steam outlet line 14 design can likewise beseen underneath the joint 15 in FIG. 2.

1-14. (canceled)
 15. A turbomachine, comprising: a rotor which ismounted such that it rotates about a rotation axis; an inner innerhousing; an outer inner housing; an outer housing; and a flow channel,wherein the inner inner housing and the outer inner housing are arrangedaround the rotor, wherein the outer housing is arranged around the innerand the outer inner housings, wherein a first flow area for a flowmedium to flow in a flow direction is formed between the inner innerhousing and the rotor, wherein a second flow area is formed between theouter inner housing and the rotor downstream from the first flow area,seen in the flow direction, wherein the outer inner housing is arrangedaround the inner inner housing only in an area of the first flow areaalong the rotation axis, wherein the flow channel, which includes aplurality of rotor blades and stator blades, is formed between the outerinner housing and the rotor, as well as between the inner inner housingand the rotor, wherein the turbomachine is a twin-flow machine, andwherein the plurality of stator blades are arranged on the inner innerhousing and on the outer inner housing.
 16. The turbomachine as claimedin claim 15, wherein a cooling steam area is formed between the innerinner housing and the outer inner housing.
 17. The turbomachine asclaimed in claim 16, wherein a flow connection is formed between thefirst and/or second flow areas and the cooling steam area, between theinner inner housing and the outer inner housing.
 18. The turbomachine asclaimed in claim 15, wherein a cooling steam outlet line, is formed fora cooling medium which is located in the cooling steam area to flow outof the cooling steam area.
 19. The turbomachine as claimed in claim 15,wherein the cooling steam outlet line is arranged in the outer innerhousing.
 20. The turbomachine as claimed in claim 19, wherein the outerinner housing comprises an outer inner housing upper part and an outerinner housing lower part.
 21. The turbomachine as claimed in claim 20,wherein the cooling steam outlet line is arranged in the outer innerhousing upper part.
 22. The turbomachine as claimed in claim 20, whereinthe cooling steam outlet line is arranged in the outer inner housinglower part.
 23. The turbomachine as claimed in claim 15, wherein theinner inner housing is formed from a nickel-based material.
 24. Theturbomachine as claimed in claim 15, wherein the inner inner housing isformed from a steel with a high chromium content, which comprises 9-10%by weight of chromium.
 25. The turbomachine as claimed in claim 24,wherein the outer inner housing is formed from a material of lesserquality than the inner inner housing.
 26. The turbomachine as claimed inclaim 15, wherein an apparatus for holding stator blades is provided inthe inner inner housing and in the outer inner housing.
 27. Theturbomachine as claimed in claim 26, wherein the apparatus is in a formof a plurality of grooves.
 28. The turbomachine as claimed in claim 15,further comprising an inlet-flow area for fresh steam, wherein the innerinner housing is arranged in an area of the inlet-flow area.